1. Field of the Invention
The present invention concerns a method of washing pipework of a filling machine or similar device.
2. Description of Related Art Including Information Disclosed Under 37 C.F.R. 1.97 and 1.98
A filling machine is a device that automatically fills bottles or cans with a liquid product.
Such a filling machine 100 is shown in the single FIGURE. It comprises a first reservoir 102 in which a first liquid product 104 is stored and a second reservoir 150 in which a second liquid product 152 is stored.
The first liquid product 104 flows from the first reservoir 102 through a first connecting pipe 106 as far as a feed pipe 114 passing through a first valve 116. The second liquid product 152 flows from the second reservoir 150 through a second connecting pipe 154 as far as the feed pipe 114 passing through a second valve 156. The first valve 116 and the second valve 156 are disposed at the feed pipe 114 and are controlled so that only one is open to allow the passage of only one liquid product 104 or 152 or so that neither is open so as to allow the washing of the pipework of the filling machine 100, as explained below.
From the feed pipe 114, the liquid product 104, 152 flows as far as a distributor 108. From this distributor 108, several filling pipes 110a, 110b, 110c and 110d extend, which are distributed so as to allow the simultaneous filling of several cans. Each filling pipe 110a, 110b, 110c, 110d terminates in a filling nozzle 112a, 112b, 112c, 112d through which the liquid product 104 flows into the can. Each filling nozzle 112a, 112b, 112c, 112d comprises an opening and closing device controlled by a control unit.
When the first liquid product 104 is to be replaced by the second liquid product 152, the first reservoir 102 must be disconnected from the feed pipe 114 by closing the first valve 116, and then the filling machine 100, and in particular the pipework extending between the feed pipe 114, the distributor 108, the filling pipes 110a, 110b, 110c and 110d and the filling nozzles 112a, 112b, 112c and 112d, must be washed in order to make all traces of the first liquid product 104 disappear before the second reservoir 152 is connected to the feed pipe 114 by opening the second valve 156.
A method of washing the pipework of the filling machine 100 is known which comprises a step of draining the first liquid product 104 through the filling nozzles 112a, 112b, 112c, and 112d, a step of filling the pipework of the filling machine 100 with a washing liquid and a step of draining the washing liquid. The step of filling with the washing liquid and the step of draining the washing liquid can be repeated several times according to the degree to which the pipework of the filling machine 100 is dirty. This method requires a large quantity of washing liquid and, according to the number of passes of this washing liquid, the washing process may be lengthy.
Another washing method is known that comprises, after closure of the first valve 116, a step of draining the pipework of the first liquid product 104 through the filling nozzles 112a, 112b, 112c and 112d, a step of filling the pipework of the filling machine 100 with a washing liquid up to a filling level referenced 120, a step of introducing at a constant rate into the pipework a volume of air through the filling nozzles 112a, 112b, 112c and 112d and a step of draining the washing liquid.
The filling step consists of filling the pipework of the filling machine 100, that is to say the filling nozzles 112a, 112b, 112c and 112d, the filling pipes 110a, 110b, 110c and 110d, the distributor 108 and the feed pipe 114 with the washing product. Filling up to the filling level 120 thus leaves free an expansion volume 122 that does not contain any washing liquid. The volume of air introduced corresponds substantially to this expansion volume 122 and the top of the feed pipe 114 is provided with a vent 118 that allows discharge of the air from the expansion volume 122. The introduction of the air at a constant rate into the washing liquid causes the latter to rise in the pipework of the filling machine 100 and in particular in the feed pipe 114. The washing liquid then fills all the feed pipe 114 through discharge of the air initially contained in the expansion volume 122 through the vent 118. The air introduced rises by the effect of Archimedes' law then in the various pipes 110a, 110b, 110c, 110d, 108 and 114 so as to discharge through the vent 118. When the volume of air rises, the washing liquid situated just above the volume of air descends just below the volume of air, which generates a to and fro movement assisting the detachment of the particles of the first liquid product 104 stuck to the walls of the pipework.
The introduction of the volume of air takes place in one go, the introduction rate and the volume of air must be determined so that the washing liquid reaches as far as the vent 118 but without overflowing. This is because an excessively violent introduction of a volume of air corresponding to the expansion volume 122 causes a rising of the washing liquid as far as the top of the feed pipe 114 but, under the effect of its inertia, the washing liquid rises higher and overflows from the feed pipe 114 through the vent 118.
Even if this washing method gives good results, it keeps certain drawbacks. For example, during this washing method, the introduction of the air generates a single to and fro movement, which may not be sufficient to detach certain particles of the first liquid product 104, which then remain fixed to the walls of the pipework. This is because the washing is all the more effective when there are several to and fro movements and the speed of introduction of the volume of air is great. Because the introduction of the volume of air takes place at a low speed, the air introduced moves in the form of bubbles and the washing process is more similar to a process of stirring the washing liquid than to a true washing method.